Tube cleaning machine



A. CARTER TUBE CLEANING MACHINE Filed D96. 3, 1934 5 Sheets-Sheet l NEma Aug. 10, 1937, A, CARTER 2,089,597

TUBE CLEANING MACHINE Filed Dec 3, 1934 5 Sheets-Sheet 2 v M 3 B mm mmmm 9+ B m N kwmwi R an R C\\ m y Berg 1 Aug. 10, 1937. .A. CARTER TUBECLE ANING MACHINE Filed Dec; 3. 1934 5 Shee ts-Sheet 3 Aug 10, 1 7- A.CARTER TUBE CLEANING MACHINE 5 Sheets-Sheet 4 Filed Dec. 3. 1934 Fig. 10

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Aug. 10, 1937. A, CARTER TUBE CLEANING MACHINE File'd Dec. 3, 1934 5Sheets-Sheet 5 v Q Q gwm @15 7Qm @fw W Patented Aug. 10, 1937 STATESPATENT OFFIQE TUBE CLEANING MACHINE Application December 3, 1934, SerialNo. 755,727

20 Claims.

This invention relates to a method of and apparatus for cleaning theinterior of tubes, and is especially concerned with a method andapparatus for removing scale from the tubes of a steam boiler or thelike. Heretofore, it has been the general practice to remove scale fromboiler tubes by using mechanism carrying brushing or cutting tools tobrush or cut the scale from the inner surfaces of the tubes. While suchmethods of cleaning tubes have been more or less successful, thebrushing or cutting tools, used in carrying out these methods, haverequired re placement at frequent intervals. Indeed, severalreplacements have been required during the cleaning of the tubes of onecomparatively small boiler. The operation of such mechanism is thereforeexpensive, due to the cost of the tools, and also because of the timelost in making the replacement. The latter is often a seriousdisadvantage in itself, as, in many instances, the cleaning of the tubesmust be accomplished while the boiler is out of operation and hence thetime required for changing or replacing the tools lengthens the idleperiod of the boiler.

Moreover, when cutting tools are used, there is danger, in case thescale is abnormally hard on one side of the tube, for the tool to assumean eccentric position in the other direction and cut away some of themetal of the tube on the opposite side, materially weakening the wallthereof. The general object of the present invention is to provide amethod and apparatus for removing scale and other foreign matter fromthe inner walls of boiler tubes and the like, in an economical,eflicient manner, with rapidity and without danger of injuring the tube.

I accomplish the object above mentioned, broadly speaking, by employinga blast of abrasive material which is directed against the interior ofthe tube. It is one of the objects of the present invention to providean apparatus for efiiciently handling such blast for progressivelycleaning the tube wall.

A further object of the invention is the provision of a mechanism whichmay be inserted within a boiler tube and provided with a nozzle or blastpassage adapted to be wobbled or oscillated by mechanism carried withinthe tool.

Another object is the provision of a tube cleaning machine, which may beinserted in a tube to be cleaned and which mechanism will remove scale,and the like, from the inner walls of the tube by directing a blast ofabrasive material at the walls through a nozzle, which is wobbled, by aportion of the blast stream through mechanism carried by the machine, sothat the blast is directed against the walls of the tube at an acuteangle thereto, and with a swirling motion.

Other objects of the invention will become more apparent from thefollowing description, reference being had to the accompanying drawings,in which I have illustrated a preferred form of mechanism for carryingout my improved method. The essential features of the invention will besummarized in the claims.

In the drawings, Fig. 1 is an elevation of a tube partially broken awayto illustrate my improved tube cleaning machine in operation; Fig. 2 isa view similar to Fig. 1, but illustrating the machine as adapted foruse in a tube of a larger diameter than that shown in Fig. 1; Fig. 3 isa vertical section as indicated by the line 3--3 on Fig. 1, illustratingmy machine in the elevation; Fig. 4 is an axial section on the forwardportion of my improved tube cleaning machine on an enlarged scale, theplane of the section being substantially parallel to the plane of Fig.1; Fig. 5 is an axial section on the rear portion of my machine, thesection being the same as that of Fig. 4, the line aa of Fig. 5 beingthe same as line a a. of Fig. 4; Fig. 6 is an axial section, asindicated by the line 6-6 of Fig. 5, the plane of such section beingnormal to the plane of Figs. 4 and 5; Figs. 7 to 10 inclusive are radialsections as indicated by the correspondingly numbered lines on Fig. 5;Figs. 11, 12 and 13 are radial sections, as indicated by the lines H! I,l2l2 and Ill-I3, respectively, of Fig. 4. Fig. 14 is a side elevationpartially in section of a modified form of my invention; Fig. 15 is asectional detail as indicated by the lines I5l5 on Fig. 14.

My improved method comprises directing a blast of abrasive material,such as sand, through a nozzle towards the internal walls of the tube tobe cleaned, and advancing the nozzle longitudinally through the tube,while causing the nozzle to direct the blast of abrasive material in aspiral path around the walls of the tube without rotating the nozzle,its supporting mechanism, or the conduits which furnish the nozzle withabrasive material and compressed air or steam which is used to providethe blast, and I prefer to utilize a portion of the compressed air orsteam to move the nozzle for obtaining the swirling action of theabrasive material.

Referring again to the drawings, and especially to Fig. 1, wherein Ihave illustrated a preferred form of apparatus for carrying out myimproved method, it will be seen that I have provided a cylindricalshaped body ID, of such diameter that it may readily be introduced intoa boiler tube, such as the tube T. Flexible conduits H and I2 areconnected to the rear end of the body. The conduit II supplies the bodywith abrasive material or grit, such as sand, which is forced into suchconduit with air or steam pressure by any suitable apparatus, notillustrated, but which is generally well known and used in the sandblasting art to conduct sand to the blasting jets. The conduit l2supplies air or steam, under pressure of about one hundred pounds to thesquare inch, to the body where it is introduced into the grit stream, aswill be hereinafter more fully explained.

At the forward end of the body is a nozzle it which is positioned at anacute angle to both the body and the tube. The nozzle is wobbled ormoved bodily in a circular path within the tube, without actuallyrotating the nozzle or the body. As neither the nozzle nor the bodyrotate within the tube, the body may be progressed longitudinallytherethrough without danger of twisting the flexible conduits H and 12.This feature also permits the body to be progressed by merely pushing orshoving the conduits into the boiler tube. The conduits, while flexible,are nevertheless semi-rigid, due to the presence of grit in one and thecomparatively great air pressure in the other.

The body l0 comprises a series of apertured cylindrical members joinedtogether, by suitable bolts it, to form an integral unit. In general,each body member has four apertures 6, l, 8 and 9, which coact withsimilar apertures in. other body members to form four longitudinally oraxially extending passageways l6, ll, I8 and Hi. The passageway I6 is incommunication with the conduit l l which supplies grit to the mechanism.The passageway ll provides chambers for an air motor and suitablereduction gearing which serve to wobble the nozzle. The passageway i8 isin communication with the air conduit l2, and introduces steam or airunder pressure, preferably the latter, to both the motor and the nozzle.The remaining passageway 19 serves as an exhaust passageway for the airmotor.

The left hand body member 2! Figs. 5, 6 and 7, serves as a cap, and isprovided with threaded openings 2i and 22, communicating withpassageways lit and I8, respectively. Suitable threaded connectormembers Ila and I211. are inserted in the openings and have attachedthereto, by any suitable clamping means (not shown) the conduits H andI2.

The air motor comprises a pair of rotors 25, secured together as a unit,as will be hereinafter more fully described, and provided withoppositely extending axial stub-shaft portions 26 which are journalledin bearings 21 and 28, carried by the body members 30 and E0,respectively.

The rotors are somewhat less in diameter than their respectivecylindrical chambers 3! of the passageway E1. The axis of each chamberis parallel with but eccentric to the axis of the rotors. Thearrangement is such that the upper portion of each rotor engages theupper wall of its respective chamber, as shown in Fig. 9.

Each rotor 25 is provided with a diametric slot 33, in which a pair ofvanes 34 are slidably mounted end to end. Suitable springs 35 areinterposed between the vanes of each pair, and retain the outer edges ofeach vane in engagement with the wall of its respective chamber 3| atall times. The two rotors are connected by a hub portion 36, of smallerdiameter than the rotors, and arranged to be embraced by a body memberwhich forms a valve controlling the intake and exhaust of air to andfrom the chambers 3|.

The body member, or valve plate 50 is best illustrated in Figs. 6 and 8.It is there shown, as provided with apertures liia, Ila, Ma and i911.which partially form the passageways, heretofore mentioned. The valveplate is provided with a lateral passageway 38, which communicates withan air pressure passageway l8, and both rotor chambers 31. A similarlaterally extending passageway 39 in the valve plate 5&3 connects thedischarge passageway HQ with both rotor chambers 3!. the chambers 3i andacting on one of the vanes 34 of each rotor, as indicated in Fig. 9,rotates the rotor in a counter-clockwise direction, until the oppositevane clears the passageway 38, at

which time the first vane will have moved into position to uncover theexhaust passageway 39. This is the usual operation of an air motor ofthis type and hence a more complete description appears unnecessary.

As heretofore mentioned, I have provided two rotors 25. The vanes of oneof these rotors are positioned at right angles to the vanes of the otherrotor. This prevents the stopping of the rotor unit in a dead centerposition and insures continuous operation Whenever air pressure isapplied through the conduit [2.

The speed of the rotors is limited by the back pressure in thepassageway i9. As shown in Fig. 6, the body cap member 20 closes one endof the passageway it, while the body member 80, which closes the otherend of such passageway, is provided with restricted openings 4|, therebymaintaining a constant back-pressure on the vanes of the rotors.

For convenience in assembling and manufacturing, the two rotors 25 areseparately made and are secured together by suitable bolts or rivets 42.The right hand rotor (Fig. 5) is provided with a reduced hub portion 43,which, when assembled, is embraced by the hollow hub portion 44 of theleft-hand rotor. By so making the rotors, the slots 33 may readily becut into the hub end of respective rotors, thereby greatly facilitatingthe manufacture of the unit.

The speed of the air motor, while somewhat limited by the back pressurein the exhaust passageway, is reduced by the use of compoundexternal-internal speed reduction gearing, which is retained within thepassageway ill, and also serves to increase the power available towobble the nozzle. As shown in Figs. 5 and 10, the forwardly extendingshaft portion 26 of the rotor unit has a reduced portion 45, the axis ofwhich is eccentric to the axis of the rotor. Rotatably mounted on thiseccentric portion of the rotor shaft is a pinion ll, which constantlymeshes with an internal gear i8 and an internal gear 19, having the samepitch diameter but one more tooth than the gear 38.

The internal gear member 58 is secured to the body member iii, and isprevented from rotation relative thereto by a key 5!. The other internalgear member 59 is rigidly secured to a shaft 52, journalled in a bearing53 in the body member 88. Every time the external gear 59 makes onecomplete revolution relative to the internal gear 58, the internal gear69 is rotated a distance equivalent to one tooth. Hence, if the gears 88and 49 are provided with I5 and i6 teeth respec- Air under pressure,therefore, enters tively a sixteen to one reduction is obtained betweenthe shaft 26 and shaft 52.

The speed of the shaft 52 is further reduced by the use of anothercompound internal-external gear reducing member. As shown, a spur gear55 is rotatably journalled on an eccentric portion 56 of the shaft 52and meshes simultaneously with internal gears 51 and 58. The gear 58 issecured against rotation in the body member 85 by a suitable key such asindicated at 59. The gear 51 is drivingly secured to a shaft member BImounted in suitable bearings 62 in the body member 90. Hence, if thegears 51 and 58 are provided with 15 and 16 teeth respectively, theresult will be a 15 to 1 reduction between the shafts 52 and 5 I.

The shaft 6| serves to wobble a bearing member 68. As shown in Fig. 4,the right-hand end of the shaft 6! is secured to a curved tube 65, theouter end of which projects forwardly, at an angle to the axis of theshaft, and has secured thereto a jet member 55. The jet is rotatablymounted in suitable bearings 61, carried by the annular bearing member68. The bearing member abuts, at one end of the tube 55, and at theother end a cap member 59 secured to and forming part of the jet 65,thereby preventing axial movement between the jet and the bearingmember.

The bearing member 68 wobbles the nozzle I4, which in turn serves toprevent rotation of the bearing member. As shown in Figs. 4 and 13, thebearing member 68 is connected with a ring II by integrally formedconnecting posts or bars 12. The nozzle I I comprises an aperturedmember 15, mounted in a retaining ring 15, which is secured to the ringH by suitable bolts 15. Threadingly secured to the right-hand bodymember IE5 is a collar I5I and similarly secured to the ring TI is acollar I02. The two collars are connected by a flexible conduit I05,comprising a metallic guard I58 and a flexible rubber or compositiontube !51. The metallic guard is preferably a flexible metal tube and isbrazed or otherwise secured to the respective collars IIlI and I52,thereby preventing rotation of the nozzle, while permitting it to wobbleabout the axis of the right-hand end of the Wobbler tube 65.

Sand is fed to the nozzle I4 through the passageway I5, whichcommunicates with an opening I09 in the body member I00, through whichthe sand or grit enters the flexible tube I55. The compressed air orsteam under pressure entering through the passageway I8, as shown inFig. 6, is fed into a chamber IIil in the body member I00 and passesthrough openings III in the hollow tube 5I which is in communicationwith the hollow tube 55 and the jet member 66. The air therefore carriesor ejects the sand through the nozzle 1A in the form of a blast.

The various bearings and shafts are lubricated with oil stored in achamber I20 within the body member 28. As shown, this body member isprovided with suitable opening adapted to be closed by a plug I2I sothat oil may be supplied to the chamber I29 from time to time. A felt orfibrous washer member I22 retains the bulk of the oil within the chamberI20, but permits the filtering or seeping of the oil into the passagewayI6, where it lubricates the various bearings and the rotor vanes. Theoil is conducted from one of the vane slots through a tubular passagewayI24 in the sub-shaft 25 0f the rotor into the chamber I25, whichcontains the reduction gearing 45, 48 and 49, from whence an axialopening I26 in I15- the shaft member 52 permits the oil to flow into thechamber I21, which encloses the reduction gearing 55, 51 and 58.Suitable oil passageways I28 in the shaft member GI permit the oil tolubricate the bearing member 62. A small passageway I29 between the airpressure conduit or passageway I8 and the oil chamber I28 equalizes thepressure on the oil.

The bearings 58 and 61 are lubricated by moisture and oil which isconveyed to the jet by the compressed air stream. As shown, a suitableopening I 39, communicating with the blast passageway I3I of the jet,and with a hollow groove or recess I33 in the bearing member permitsmoisture to enter and lubricate such bearing.

The body, as shown in Fig. 1, is slightly smaller than the internaldiameter of the tube T. To adapt the body to larger diameter tubes, suchis illustrated at T in Fig. 2, I prefer to provide a carriage, such asis shown in Figs. 2 and 3, and which maintains the body substantially inthe center of the tube and thereby enables the grit to act against theinner wall of the tube with substantially the same force in anydirection.

The carriage comprises a pair of bands I42) arranged to be clamped inposition on the body. Pivoted to each band I 35 are a series ofequispaced links IlII. Each link is pivoted at one end to its respectivering and at the other end carries a roller I52 adapted to engage theinner walls of the tube. The corresponding links Id! of each ring I48are pivoted together intermediate their ends, as at I44. Hence, byadjustably positioning the clamping rings axially of the body, thecarriage may readily be adjusted for different diameters of tubes.

As heretofore described, my improved tube cleaner utilizes a blast ofabrasive material, such as sand or mineral grit for cleaning tubes.Materials such as these are apt to cause premature wear on the walls ofthe grit passageway I 5. In the form of the invention illustrated, inFigs. 1 to 13 inclusive, the grit passageway I6 is formed integral withthe body members 38, 50, 50, 65, 10, 80 and 90. Hence, in event ofexcessive wear, due to the use of certain grits, such members mightrequire replacement. I therefore may prefer to provide a grit passagewayindependent of such body members. Such an independent passagewayeliminates the entrance of grit in the air motor and gear reductionmechanism in event of complete erosion of the walls of the passageway.

In Figs. 14 and 15 I illustrate a modified form of body provided with aseries of body members similar to the correspondingly numbered bodymembers heretofore described. In this instance, however, theintermediate body members each have recesses I10 formed in their outerwalls. Such recesses are aligned to form a channel I'II arranged toreceive a removable tubular member I12 having walls formed complementarywith the walls of the channel HI and an outer wall forming substantiallya continuation of the cylindrical contour of the body. The ends of thetube I12 about the openings 6 in the body members 20 and I00, suitablegaskets I15 being interposed therebetween to insure a tight jointconsequent upon the clamping of the tube in position by the tighteningof the body bolts I5. This, therefore, eliminates replacementrequirements for the intermediate body parts and their complicatedmechanisms.

From the foregoing description it will be seen that I have provided asimple yet effective method of economically cleaning the inner walls ofboiler tubes, without danger of injuring them, by applying a sand blastto the walls through a mechanism which may be inserted and fed throughthe tube to be cleaned, and I have provided a, mechanism for causing thesand to be applied with a spiraling motion, which mechaanism may beinserted in tubes of comparatively small diameters, and which mechanismcontains. a power unit and reduction gearing to wobble a sand blastnozzle, while preventing actual rotation of the machine itself, thenozzle or connecting conduits.

I claim:

1. A mechanism for cleaning tubes, comprising a body adapted to bewholly inserted in the tube to be cleaned, conduit means communicatingwith the body, a nozzle carried by the body, means for ejecting a blastof abrasive material through the nozzle toward the wall of the tube tobe cleaned, and power operated means carried by said body and reactingthereon to move the nozzle relative to the body and transversely of thetube.

2. A mechanism for cleaning tubes, comprising a body adapted to bewholly inserted in the tube to be cleaned, a conduit communicating withthe body, a nozzle carried by the body, means carried by the body andcommun cating with said conduit to eject an abrasive material from saidbody towards the wall of the tube, and a power-operated mechanismcarried by said body to move the nozzle relative to the body while thebody is being progressed through the tube.

3. A mechanism for cleaning tubes comprising a body adapted to beinserted wholly in the tube to be cleaned, a conduit for abrasivematerial connecting the body, a nozzle movably carried by the body,means to cause an abrasive material to be ejected from the nozzle towardthe wall of said tube, and means operated by said last-named means tomove said nozzle relative to the body.

4-. A mechanism for cleaning tubes comprising a body adapted to beinserted wholly in the tube to be cleaned, a conduit for abrasivematerial connecting with the body, a pressure conduit communicating withthe body, a nozzle carried by the body and communicating with both ofsaid conduits to cause an abrasive material to be ejected from thenozzle, and a motor carried by said body to continuously move thenozzle.

5. A mechanism for cleaning tubes comprising a body adapted to beinserted in the tube to be cleaned, a conduit for abrasive materialconnecting the body, a pressure conduit communicating with the body, anozzle carried by the body, a jet mechanism carried by the body andcommunicating with both of said conduits to cause an abrasive materialto be ejected from the nozzle, an air motor operated from air pressureand carried within said body to move the nozzle, and means to maintainthe nozzle at an acute angle to the wall of the tube being cleaned.

6. A mechanism for cleaning tubes, comprising a body adapted to beinserted in the tube to be cleaned, a conduit communicating with thebody, a nozzle carried by the body whereby material may be ejected fromthe body toward the Wall of the tube, reduction gearing mounted in saidbody, and power operated mechanism for applying power to said reductiongearing to move the nozzle continuously.

'7. A mechanism for cleaning tubes, comprising a body adapted to beinserted in the tube to be cleaned, a conduit communicating with thebody, a nozzle carried by the body, whereby material feed to the bodythrough said conduit may be ejected from the body toward the wall of thetube, and a power-operated mechanism mounted in said body to wobble thenozzle relative to the tube to be cleaned.

8. A mechanism for cleaning tubes, comprising a body'member adapted tobe inserted in the tube to be cleaned, a flexible conduit communicatingwith the body and adapted to convey an abrasive material thereto, asecond flexible conduit communicating with the body and adapted toconvey air under pressure thereto, a nozzle carried by said body throughwhich abrasive material is ejected from the body in the form of a blastby air pressure, an air motor, and means operated by a portion of theair pressure to cause a wobbling movement to be imparted to said nozzle.

9. A mechanism for cleaning tubes, comprising a body member adapted tobe inserted in the tube to be cleaned, a conduit communicating with thebody and adapted to convey an abrasive material thereto, a secondconduit communicating with the body and adapted to convey air underpressure thereto, a nozzle, means whereby the abrasive material isejected from the nozzle by air under pressure, an air motor, meansoperated thereby to impart a wobbling movement to said nozzle, saidlast-named means including a speed reducing gearing and. a webbleroperatively connected to such gearing and to said nozzle.

10. A mechanism for cleaning boiler tubes and the like, comprising aseries of apertured members secured together to form a body having aplurality of axial passageways, a flexible conduit adapted to convey anabrasive material to one of said passageways, a flexible conduit adaptedto convey a blast to another of said passageways, a motor mounted inanother of said passageways, a communication between said motor and saidblast, whereby said blast operates said motor, reduction gearingoperatively connected with said motor and carried in said lastnamedpassageway, a hollow shaft operatively connected to said gearing andcommunicating with said blast passageway, a jet carried by said shaft, anozzle spaced from said jet and in communicationwith the abrasive andblast passageways, bearing interposed between said shaft and saidnozzle, said bear lg coacting with a portion of said shaft projecting atan angle to the main portion thereof, a flexible connection between thenozzle and the body adapted to prevent relative rotation therebetween,whereby said nozzle is caused to wobble when the blast stream is fed tothe body without rotating the body or the nozzle or the conduitsrelative to the tube to be cleaned.

11.A mechanism for cleaning tubes, comprising a body member, a nozzlemovably carried by said body and through which abrasive material may beejected toward the walls of the tube, and a flexible metal conduitconnecting the nozzle with said body and forming a passageway forabrasive material. said tube being lined with a flexible compositionmaterial.

12. A mechanism for cleaningtubes comprising an elongated body, an airmotor and reduction gearing mounted in substantial ain'al alignment witheach other in said body, a lubricant reservoir, a lubricant passagewaythrough said motor and said gearing, a fibrous washer disposed betweenthe lubricant passageway and said lubricant chamber, a pressure conduitin said body and a passageway communicating with said chamber and thepressure conduit to force a lubricant through said lubricant passagewayto lubricate the motor and the gearing.

13. A mechanism for cleaning tubes comprising a substantiallycylindrical body member having a longitudinal recess in its outer walland adapted to be inserted in a tube to be cleaned, a conduit for anabrasive material connected to one end of said body, a nozzle at theother end of the body and through which abrasive material is directedtoward the walls of the tube to be cleaned, nozzle operating mechanismwithin said body, means communicating with said nozzle and said conduit,said last-named means comprising a member removably inserted in the bodyrecess.

14. An apparatus for cleaning tubes comprising a nozzle adapted to beinserted into the tube to direct an abrasive blast against its interiorsurface, a support for the nozzle and means reacting on the support towobble the nozzle without rotating it.

15. An apparatus for cleaning tubes comprising a nozzle adapted to beintroduced into such tube, means for ejecting a blast of abrasivematerial from the nozzle, means adapted to be advanced through the tube,arranged for supporting the nozzle with its operating axis directed atan acute angle to the tube surface, and means reacting on the supportand operatively connected with the nozzle to wobble it about.

16. An apparatus for cleaning tubes comprising a nozzle adapted to beintroduced into such tube, a conduit adapted to feed abrasive materialthrough the nozzle under pressure, means to guide the nozzle foradvancement along the tube, and means to impart a wobbling motion to thenozzle without rotating the conduit.

17. A tube cleaning tool having a nozzle and supporting body therefor,and means reacting on the body to cause the nozzle to wobble in a fixedconical path.

18. A mechanism for cleaning tubes, comprising a body adapted to bewholly inserted in the tube to be cleaned, conduits communicating withthe body, a nozzle carried by the body, means to progressively move thenozzle so that its axis follows a substantially conical path relative tothe body, and means for ejecting a blast of abrasive material throughthe nozzle toward the wall of the tube to be cleaned.

19. A mechanism for cleaning tubes, comprising a body adapted to bewholly inserted in the tube to be cleaned, a nozzle carried by the body,means toeject a blast of abrasive material from said nozzle towards thewall of the tube to be cleaned, means to maintain the nozzle at an acuteangle relative to the axis of the tube, and power mechanism carried bysaid body and means connecting said mechanism to the nozzle to move thenozzle circumferentially of the tube during the ejection of said blastof abrasive material.

20. A mechanism for cleaning tubes of varying diameters comprising abody adapted to be inserted wholly in the tube to be cleaned, means forsupplying air under pressure and abrasive material to the body, a nozzlecarried by the body whereby the abrasive material may be ejected fromthe nozzle toward the wall of said tube, and adjustable centering meansarranged to continuously engage the tube at three spaced pointscircumferentially of the tube and on the inside thereof to maintain thebody axially located relative to the wall of the tube.

ALBERT CARTER,

